Advanced Functional Materials

Cover image for Vol. 15 Issue 9

September, 2005

Volume 15, Issue 9

Pages 1391–1554

    1. Cover Picture: Hierarchically Organized Superstructure Emerging from the Exquisite Association of Inorganic Crystals, Organic Polymers, and Dyes: A Model Approach Towards Suprabiomineral Materials (Adv. Funct. Mater. 9/2005)

      Y. Oaki and H. Imai

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200590031

      K2SO4/polymer/dye superstructures with hierarchical ordering at six different size scales can be prepared via a simple biomimetic route. The superstructures consist of five tiers from the nanoscopic to the macroscopic scale (see Figure and cover), and the incorporated dye molecules generate an additional hierarchy at the nanoscopic scale. Control of the emergent superstructure and its properties can be easily achieved by changing the polymer concentration.

    2. Photoswitchable Spirobenzopyran- Based Photochemically Controlled Photonic Crystals (pages 1401–1406)

      M. Kamenjicki Maurer, I. K. Lednev and S. A. Asher

      Version of Record online: 2 AUG 2005 | DOI: 10.1002/adfm.200400070

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      A photochemically controlled photonic-crystal material is reported. Spirobenzopyran-functionalized polymerized crystalline colloidal arrays show reversible photoswitching behavior as a consequence of spiropyran-to-merocyanine interconversion (see Figure). The system described here could be utilized for slow switching applications such as optical memory devices.

    3. Hierarchically Organized Superstructure Emerging from the Exquisite Association of Inorganic Crystals, Organic Polymers, and Dyes: A Model Approach Towards Suprabiomineral Materials (pages 1407–1414)

      Y. Oaki and H. Imai

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200500025

      Thumbnail image of graphical abstract

      K2SO4/polymer/dye superstructures with hierarchical ordering at six different size scales can be prepared via a simple biomimetic route. The superstructures consist of five tiers from the nanoscopic to the macroscopic scale (see Figure and cover), and the incorporated dye molecules generate an additional hierarchy at the nanoscopic scale. Control of the emergent superstructure and its properties can be easily achieved by changing the polymer concentration.

    4. Facile Preparation of a Patterned, Aminated Polymer Surface by UV-Light-Induced Surface Aminolysis (pages 1415–1425)

      P. Yang, X. X. Zhang, B. Yang, H. C. Zhao, J. C. Chen and W. T. Yang

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200400335

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      Tertiary amines have been incorporated onto polyester surfaces with micrometer precision using UV-light-induced surface aminolysis. The patterned immobilization of immunoglobulin (IgG) and horseradish peroxide (HRP) is achieved by the electrostatic self-assembly of these proteins onto the patterned, aminated surfaces (see Figure).

    5. Supramolecular Organization in Fluorene/Indenofluorene– Oligothiophene Alternating Conjugated Copolymers (pages 1426–1434)

      M. Surin, P. Sonar, A. C. Grimsdale, K. Müllen, R. Lazzaroni and P. Leclère

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/adfm.200500241

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      Alternating conjugated copolymers containing fluorene or indenofluorene units and oligothiophene segments are studied. Atomic force microscopy images of the morphology of thin deposits are interpreted in terms of supramolecular organization by molecular modeling. It is shown that, depending on the molecular architecture, the copolymers organize either into fibrillar structures (see Figure) or into untextured aggregates.

    6. Soft-Contact Optical Lithography Using Transparent Elastomeric Stamps and Application to Nanopatterned Organic Light-Emitting Devices (pages 1435–1439)

      T.-W. Lee, S. Jeon, J. Maria, J. Zaumseil, J. W. P. Hsu and J. A. Rogers

      Version of Record online: 20 JUL 2005 | DOI: 10.1002/adfm.200500109

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      Transparent elastomeric molds of poly(dimethylsiloxane) (PDMS) can be used as photomasks to produce either the same resist pattern as the recessed regions of the stamps or patterns of the edge. The difference in effective exposure dose between the contact and non-contact regions of the masks is used to make these two different patterns. The Figure shows a simulation plot of the near-field surface intensity through a PDMS phase mask.

    7. Low-Temperature Formation of Well-Aligned Nanocrystalline Si/SiOx Composite Nanowires (pages 1440–1444)

      T.-C. Wong, C.-C. Yu and J.-J. Wu

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200400307

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      Hot-filament chemical vapor deposition is used to prepare well-aligned nanocrystalline Si/SiOx composite nanowires (see Figure) on various substrates at 120 °C using SiCl4/H2. Water vapor from the chamber wall plays a crucial role in forming the well-aligned nanowires. A mechanism for the nanowire formation is suggested.

    8. Low-Duty-Ratio Patterning on a Heterogeneous Surface (pages 1445–1450)

      D. H. Kim, M. J. Kim, J.-Y. Park and H. H. Lee

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adfm.200500137

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      Low-duty-ratio patterns on a heterogeneous surface are made, the production of which has proven to be a challenge for mold-based lithography. The hetero-geneity of the surface arises from the difference in interfacial potential between two types of surfaces. No external force is applied, and only the natural forces associated with capillarity and dewetting are responsible for the patterning. As a result, defect-free and uniform patterning is possible over large areas (see Figure).

    9. A Light-Blue Phosphorescent Dendrimer for Efficient Solution-Processed Light-Emitting Diodes (pages 1451–1458)

      S.-C. Lo, G. J. Richards, J. P. J. Markham, E. B. Namdas, S. Sharma, P. L. Burn and I. D. W. Samuel

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adfm.200400560

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      A dendrimer that emits sky-blue light has been produced by introducing ethane links between biphenyl-based dendrons and a fac-tris[2-(2,4-difluorophenyl)pyridyl)]iridium(III) core (see Figure). Bilayer devices with blended emissive layers exhibit external quantum efficiencies of up to 10.4 % at 100 cd m–2. Dendrimes are shown to be a useful route to spin-coating short-wavelength electrophosphorescent materials for efficient solution- processed LEDs.

    10. Multisegment PtRu Nanorods: Electrocatalysts with Adjustable Bimetallic Pair Sites (pages 1459–1464)

      F. Liu, J. Y. Lee and W. J. Zhou

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adfm.200400523

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      Multisegment (PtRu) nanorods (see Figure) have been studied by obtaining current–time plots recorded at room temperature. The linear relationship between the number of Pt–Ru interfaces and catalytic activity unambiguously demonstrates the existence of bimetallic pair sites and a bifunctional mechanism in direct methanol fuel-cell anode reactions.

    11. Formation of Nanoislands on Conducting Poly(3,4-ethylenedioxythiophene) Films by High-Energy-Ion Irradiation: Applications as Field Emitters and Capacitor Electrodes (pages 1465–1470)

      J. Joo, S.-K. Park, D.-S. Seo, S.-J. Lee, H.-S. Kim, K.-S. Ryu, T.-J. Lee, S.-H. Seo and C.-J. Lee

      Version of Record online: 2 AUG 2005 | DOI: 10.1002/adfm.200500019

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      Poly(3,4-ethylenedioxythiophene) (PEDOT) nanoislands (see Figure) have been directly fabricated on the surface of films using high-energy-ion irradiation. The nanoislands form due to micelle formation of a polymeric stabilizer. Increase of the emitter current density in field-emission displays and of capacitance in cyclic voltammetry using PEDOT nanoislands are observed.

    12. ZnSe–Si Bi-coaxial Nanowire Heterostructures (pages 1471–1477)

      C. R. Wang, J. Wang, Q. Li and G.-C. Yi

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200400564

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      ZnSe/Si bi-coaxial nanowires (see Figure) and secondary nanostructures of ZnSe nanobrushes or a SiOx sheath grown on the primary bi-coaxial nanowires have been prepared on silicon substrates by the one-step thermal evaporation of ZnSe powder. The bi-coaxial nanowire heterostructures exhibit a clean interface between ZnSe and silicon. The experimental evidence strongly suggests that the bi-coaxial nanowires are formed via a co-growth mechanism.

    13. Silicon Nanowire Sensors for Bioanalytical Applications: Glucose and Hydrogen Peroxide Detection (pages 1478–1482)

      M.-W. Shao, Y.-Y. Shan, N.-B. Wong and S.-T. Lee

      Version of Record online: 20 JUL 2005 | DOI: 10.1002/adfm.200500080

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      Silicon nanowire films (see Figure) modified with boron are used as sensors to monitor glucose in aqueous solution. The sensors have a wide linear detection range and exhibit high sensitivity. They also show good reproducibility and long-term stability. Silicon nanowire films have also been modified with magnesium and used to detect hydrogen peroxide in aqueous solution.

    14. 1-Methyl-2-(anthryl)-imidazo[4,5-f][1,10]-phenanthroline: A Highly Efficient Electron-Transport Compound and a Bright Blue-Light Emitter for Electroluminescent Devices (pages 1483–1487)

      R.-Y. Wang, W.-L. Jia, H. Aziz, G. Vamvounis, S. Wang, N.-X. Hu, Z. D. Popović and J. A. Coggan

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200500041

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      Efficient electron-transport materials are important for the development of high-performance organic light-emitting diodes. The title compound, a colorless organic molecule with strong intermolecular interactions (see Figure), is shown to be a bright blue-light emitter and a highly efficient electron-transport material in electroluminescent devices.

    15. Bio-inspired Synthesis of Protein-Encapsulated CoPt Nanoparticles (pages 1489–1494)

      M. T. Klem, D. Willits, D. J. Solis, A. M. Belcher, M. Young and T. Douglas

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200400453

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      CoPt nanoparticles in protein cages have been synthesized (see Figure) by genetically altering the small heat-shock protein cage from Methanococcus jannaschii to display a dodecapeptide, which has a strong affinity for the L10 phase of CoPt, on the interior surface. The CoPt particles are size constrained, and the cages are shown to be robust under a wide range of synthetic conditions.

    16. High-Performance Polyaniline Prepared via Polymerization in a Self-Stabilized Dispersion (pages 1495–1500)

      S.-H. Lee, D.-H. Lee, K. Lee and C.-W. Lee

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200400467

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      An improved synthetic method has been developed for the preparation of highly conducting and soluble polyanilines. They have been prepared in a self-stabilizing dispersion mode utilizing an aqueous/organic biphase system and have a porous particle morphology (see Figure, magnification ×30 000). The new polyaniline has a conductivity exceeding 600 S cm–1.

    17. Nanofluids: A New Class of Materials Produced from Nanoparticle Assemblies (pages 1501–1510)

      R. Jagannathan and G. C. Irvin Jr.

      Version of Record online: 20 JUL 2005 | DOI: 10.1002/adfm.200400474

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      Organic nanoparticle assemblies (1–10 nm in size) are produced by a compressed-CO2-expansion process (see Figure). The assemblies have narrow particle size distributions and display novel fluid-like properties (hence termed “nanofluids”). They also exhibit optical properties that are tunable by the expansion process, and could find use as a new class of liquid conductors, or in liquid ceramics and nanobearings.

    18. Conductive SU8 Photoresist for Microfabrication (pages 1511–1516)

      S. Jiguet, A. Bertsch, H. Hofmann and P. Renaud

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adfm.200400575

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      Microelectrode arrays have been fabricated (see Figure) photolithographically, using a conductive composite photoresist containing a dispersion of silver nanoparticles. The composite structures made have a resolution of better than 5 μm and a maximum aspect ratio of 5. They show a wide range of electrical conductivity, which is dependent on the silver volume fraction. A soft thermal treatment can further enhance the conductivity by one order of magnitude.

    19. Influence of Molecular Weight on the Surface Morphology of Aligned, Branched Side-Chain Polyfluorene (pages 1517–1522)

      M. Knaapila, B. P. Lyons, T. P. A. Hase, C. Pearson, M. C. Petty, L. Bouchenoire, P. Thompson, R. Serimaa, M. Torkkeli and A. P. Monkman

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adfm.200500061

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      The relationship between macroscopic–submicrometer-scale morphology and self-organized intermolecular structure and uniaxial alignment is highlighted for a series of poly(9,9-bis(ethylhexyl)-fluorene-2,7-diyl) films. At a threshold molecular weight, there is a distinct transition in morphology (see Figure: left panel: nematic phase; right panel: hexagonal phase).

    20. Synthesis of Spheres with Complex Structures Using Hollow Latex Cages as Templates (pages 1523–1528)

      M. Yang, J. Ma, Z. Niu, X. Dong, H. Xu, Z. Meng, Z. Jin, Y. Lu, Z. Hu and Z. Yang

      Version of Record online: 5 AUG 2005 | DOI: 10.1002/adfm.200500070

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      Various hollow spheres with complex structures, such as pillared hollow spheres (see Figure) and double-shelled hollow spheres, have been prepared by using hollow latex cages as templates. This new template synthesis provides a simple approach for easily controlling the morphology of hollow spheres by altering the loading sequence of the reagents and their concentration.

    21. Microtribological and Nanomechanical Properties of Switchable Y-Shaped Amphiphilic Polymer Brushes (pages 1529–1540)

      M. C. LeMieux, Y.-H. Lin, P. D. Cuong, H.-S. Ahn, E. R. Zubarev and V. V. Tsukruk

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adfm.200500088

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      Nanoscale reorganization affects the adhesion and elastic properties of surface-grafted, binary polystyrene–poly(acrylic acid) brushes (PS-PAA). These amphiphilic, Y-shaped brushes (see Figure) exhibit a dramatic variation in friction and wear properties after exposure to solvents specific for different arms (toluene and water for PS and PAA, respectively), showing a lower frictional coefficient and higher wear stability after water treatment.

    22. Synthesis and Characterization of n-Type Materials for Non-Doped Organic Red-Light-Emitting Diodes (pages 1541–1546)

      S. Y. Chen, X. J. Xu, Y. Q. Liu, G. Yu, X. B. Sun, W. F. Qiu, Y. Q. Ma and D. B. Zhu

      Version of Record online: 29 AUG 2005 | DOI: 10.1002/adfm.200500105

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      Two compounds with intramolecular charge transfer, which show great potential for use as n-type red-light-emitting materials, have been designed and synthesized. Three types of non-doped red-light-emitting diodes are studied using these two compounds as the electron-transporting (see Figure) and host-light-emitting layers, respectively. One device has pure red electroluminescence with an external quantum efficiency of 0.7 % under ambient conditions.

    23. Plastic Solar Cells Based on Fluorenone-Containing Oligomers and Regioregular Alternate Copolymers (pages 1547–1552)

      R. Demadrille, M. Firon, J. Leroy, P. Rannou and A. Pron

      Version of Record online: 25 JUL 2005 | DOI: 10.1002/adfm.200500117

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      Oligomers and regioregular copolymers based on fluorenone subunits (see Figure) have been synthesized and used in polymer/fullerene bulk-heterojunction photovoltaic cells (see Figure). Incident photon-to-current conversion efficiency experiments show that the fluorenone units are efficient in converting photons to electrons. Some of the devices exhibit efficiencies (ηext) of up to 1.1 %.

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